Run a temp line to see if the meter reads the same. If not replace the line. The XM1/2 is helpful however nothing works better than running new lines. Suckout when you say you changed fittings was that inside and outside the ones you can see, what about the ones you can’t?
wave every time I ran into this the line was open somewhere i.e animal chewed on it and line is open, cut by weed wacker lines is open however it’s still sending signal.